76 



disappear with the development of the bunch-grass into a closed as- 

 sociation. They depend for space upon the tuft-like growth-form 

 of the bunch-grasses, in the same manner as do the slender annual 

 plants of the association, the interstitial plants. The animals of the 

 bare sand spaces have accordingly been called interstifial animals. 

 The tiger-beetles are very good examples of this group. The large 

 animals are not influenced to any considerable extent by these ex- 

 tremely local differences between grass tufts and bare spaces, and 

 so the interstitial group is composed only of the smaller animals, 

 Cnemidophorus being the only vertebrate. This relation of the small 

 animals to the plants is important, for it illustrates one of the ways 

 in which the animals are influenced by the plants. The interstitial 

 group serves further as a convenient index to the relations between 

 the bunch-grass and other associations of the sand prairie. 



Subterricoloiis Predaceous Animals. — Although a number of ani- 

 mals are burrowing forms, their principal activities are carried on 

 at or above the surface, so that the number of strictly subterranean 

 animals is greatly limited. 



Pasimachns elongatus Meloidae, larvse 



Geopinns incrassatus *Scalopns aquaticus machrinns 



Carabidac, larvae Blarina hrevicaudis? 

 Histeridae, larvae 



PARASITIC ANIMALS OF THE BUNCH-GRASS 



The parasitic bunch-grass animals are very poorly represented in 

 the collections, as appears from the following scanty list. 



Parasite Host 



Troinhidimn lociistaruni Acridiidae 



Anthrax spp., larvae Acridiidae ; Lepidoptera, larvae 



Systoechtts vulgaris, larvae Acridiidae, eggs 



Gonia front osa, larvae Lepidoptera, larvae 



Spalanzania sp., larvae Lepidoptera, larvae 



Apanteles theclae Lepidoptera, larvae 



Urios vestali Pheidole zinelandica 



None of the bunch-grass animals were examined for internal 

 parasites. A search would probably have revealed the following 

 forms : Trichonynipha gracilis Leidy, a flagellate, very abundant in 

 termites; Hirmocystis rigida Hall, a gregarine, occurring in from 

 15 to 90 per cent, of Melanopli, wherever examined; several genera 



